Objective To compare pituitrin resuscitation,hypertonic saline resuscitation versus hydroxyethyl starch (HES) resuscitation during the early stage in a dog model of severe uncontrolled hemorrhagic shock (UHS).Methods Adult Chinese rural dogs of both sexes,weighing 10-12 kg,underwent sever UHS by transecting one branch of mesenteric arteries,followed by blood withdrawal via the femoral artery to target mean arterial pressure (MAP) of 50 mm Hg.Twenty-four dogs with severe UHS were randomized into 3 groups according to resuscitation strategies (n =8 each):pituitrin resuscitation group (group P),hypertonic saline resuscitation group (group SA),and resuscitation with HES (group HES).In group P,pituitrin was infused at a rate of 0.04U· kg-1 · min-1 after a loading dose of 0.1 U was given intermittently.A single bolus of 7.5 ％ hypertonic saline 6 ml/kg was injected in group SA.HES 200/0.5 was infused at a rate of 18-38 ml· kg-1· h-1 in group HES.MAP was maintained no lower than 50 mm Hg in each group.The branch of mesenteric arteries was ligated 1 h after resuscitation and all the blood initially shed was returned in each group.The parameters of hemodynamics were recorded before UHS (T0),after successful UHS (T1),at 15,30,45 and 60 min of resuscitation (T2-5),and at 2 h after hemostasis and return of shed blood (T6).Arterial blood samples were taken at T0,T1,T5 and T6 for blood gas analysis.Venous blood samples were collected at T0,T5,T6 and 3 days after extubation for determination of serum TNF-α,IL-10 and adrenocorticotropic hormone (ACTH) concentrations.TNF-α/IL-10 ratio was calculated.The survival rate was measured within 72 h after hemostasis and return of shed blood.The volume of blood loss was recorded during UHS phase and uncontrolled bleeding resuscitation phase.Results Compared with group P,SBP,DBP,CVP,HR,serum TNF-α concentration and TNF-α/IL-10 ratio were significantly increased,and Hct and serum IL-10 concentration were decreased in group SA,and SBP,HR,Lac,TNF-α and ACTH concentrations,and TNF-α/IL-10 ratio were significantly increased,and serum IL-10 concentration was decreased in group HES (P ＜ 0.05).SBP,DBP,CVP,HR and serum IL-10 concentration were significantly lower,and Lac,TNF-α and ACTH concentrations,and TNF-α/IL-10 ratio were higher in group HES than in group SA (P ＜ 0.05 or 0.01).The volume of blood loss recorded during uncontrolled bleeding resuscitation phase was significantly larger in group SA than in P and HES groups (P ＜ 0.05).There was no significant difference between P and HES groups in the volume of blood loss recorded during uncontrolled bleeding resuscitation phase (P ＞ 0.05).There was no significant difference in the survival rate between the three groups (P ＞ 0.05).Conclusion Resuscitation with continuous infusion of a small dose of pituitrin can maintain the blood pressure stable with less blood loss and inhibit stress responses and inflammatory responses,and the efficacy is superior to that of resuscitation with a small dose of hypertonic saline or HES resuscitation.